This disclosure concerns utilizing two-dimensional (2D) hexagonal boron nitride (h-BN) nanosheets as the planar-alignment agent in an electro-optical liquid crystal (LC) device and thereby improving its optical transmission.
This disclosure concerns methods for achieving planar-alignment of liquid crystal (LC) employing two-dimensional (2D) hexagonal boron nitride (h-BN) nanosheets in an electro-optic LC device.
This disclosure concerns procedures for attaining electro-optic switching of an LC in this h-BN-based LC device.
A novel product is described herein with an h-BN-based LC device that exhibits more optical transparency than a regular polyimide (PI) alignment layer-based LC device.
Liquid crystals (LCs) are optically anisotropic materials, and they are widely used in electro-optical display technology. Understanding the alignment phenomena of a nematic LC on a surface remains an important area of research, as the alignment process determines the LC's molecular orientation and conformation—which influence the LC's optical and electro-optical characteristics.
Semi-transparent LC cells are used in optically transmissive liquid crystal displays (LCDs), where the planar-alignment layers are utilized to create an easy axis of the nematic director ({circumflex over (n)}) of the LC.
The conventional planar-alignment agent is a rubbed polyimide (PI)-coated surface. On the unidirectionally rubbed PI alignment substrate, the LC molecules align with alkyl side chains along the rubbing direction, creating a uniform planar director profile on the substrate.
However, the conventional rubbed PI alignment process has some disadvantages. The temperature during the rubbing process of the PI has a significant impact on the LC alignment. The occurrence of fiber dust during the rubbing process of the PI contaminates the LC. Uneven rubbing creates a wide distribution of pre-tilt angles of the LC—which causes a non-uniform brightness in the LCD panel. The PI alignment layers can inject free ion impurities into the LC.
Therefore, there is a long-standing need to find alternative alignment agents for LCDs.
Here, we demonstrate the first use of the two-dimensional (2D) hexagonal boron nitride (h-BN) as the planar-alignment agent in an electro-optic LC device.
This h-BN-based LC device shows the required electro-optic effect for an LCD. This electro-optic device also shows higher optical transparency than a regular PI alignment layer-based LC device.
Replacing the PI alignment layers with h-BN nanosheets effectively reduces the thickness of all the alignment layers 120 nm to less than 1 nm. For electro-optic devices, the order of magnitude reduction in path length through absorbing layers makes it possible to achieve higher optical throughput.